This day my garmin edge show warning about trainer need to calibrate. I tried calibration using garmin edge but always show error message. Try another method , using magene utility show same result, always getting error result when doing speed calibration.
On magene utility showed some link to video on chinese languange how to tighten the belt using 5 mm and 3 mm allen key, but the information not to detail how to do it.
Base on wahoo kicker core video , I open trainer bottom case cover using allen key 2 mm and some plus screw driver , total there four bolt. Since gravat 2 design like wahoo kicker core , I untight the 5 mm bolt first then tight the 3 mm , it will made belt became tight and I did another calibration and now calibration successfully.